Explain how nitrification affects alkalinity, and what is the typical impact per unit of NH4+-N oxidized?

Explain how nitrification affects alkalinity, and what is the typical impact per unit of NH4+-N oxidized?

• A. Nitrification increases alkalinity.
• B. Nitrification consumes alkalinity, roughly 7 mg/L as CaCO3 per 1 mg/L NH4+-N oxidized.
• C. Nitrification has no effect on alkalinity.
• D. Nitrification converts alkalinity to nitrate directly.

Answer: (B)

Nitrification consumes alkalinity. As ammonium is oxidized to nitrate, hydrogen ions are produced, and the buffering capacity (alkalinity) must neutralize these acids, so alkalinity is depleted. A common rule of thumb is that for each 1 mg/L of NH4+-N oxidized, about 7 mg/L as CaCO3 of alkalinity is consumed. This loss of alkalinity reduces the system’s buffering and can lower pH, so alkalinity often needs to be replenished (for example with bicarbonate) to sustain nitrification.

Nitrification consumes alkalinity. As ammonium is oxidized to nitrate, hydrogen ions are produced, and the buffering capacity (alkalinity) must neutralize these acids, so alkalinity is depleted. A common rule of thumb is that for each 1 mg/L of NH4+-N oxidized, about 7 mg/L as CaCO3 of alkalinity is consumed. This loss of alkalinity reduces the system’s buffering and can lower pH, so alkalinity often needs to be replenished (for example with bicarbonate) to sustain nitrification.